In the related art, a ¼ wavelength plate formed of a sheet of a retardation plate has a problem of poor visibility. Since a wavelength imparting a phase difference of ¼ wavelength is limited to a specific wavelength, anti-reflection performance cannot be sufficiently obtained at wavelengths other than the vicinity of the specific wavelength imparting a phase difference of ¼ wavelength so that a display or the like appears as if it were colored in blue, purple, red, or the like in a case where the ¼ wavelength plate is used as an anti-reflection filter for suppressing surface reflection of a display or the like.
For this problem, a retardation plate formed by laminating a plurality of retardation plates such that the optical axes thereof intersect with each other has been proposed (PTLs 1 to 3). For example, according to PTL 2, it has been reported that, in a case where the wavelength characteristics of a retardation plate are defined using a phase difference ratio represented by a ratio Re (450)/Re (550) of a phase difference Re (450) at a wavelength of 450 nm to a phase difference Re (550) at a wavelength of 550 nm, excellent anti-reflection performance can be obtained when a retardation plate formed by laminating two retardation plates, which are one retardation plate having a phase difference ratio of 1.16 and another retardation plate having a phase difference ratio of 1.025, is used. Further, according to PTL 3, it has been reported that excellent anti-reflection performance can be obtained when a retardation plate formed by laminating two retardation plates, both of which have a phase difference ratio of 1.005, is used.
However, in all cases of the retardation plates of PTLs 1 to 3, the wavelength region imparting a phase difference of ¼ wavelength is not sufficiently wide and the wavelength region imparting excellent anti-reflection performance is also not sufficiently wide in a case where a circularly polarizing plate is produced by laminating a polarizing plate on any of these retardation plate. As the result, the visibility of a display or the like which includes the retardation plate or the circularly polarizing plate is not sufficiently improved. Specifically, a slight amount of reflected light which cannot be prevented when the display or the like is observed from an oblique direction is always generated, but there is a problem in that the slight amount of reflected light does not appear achromatic but appears as if the light were colored in blue, purple, red, or the like. This coloration means that the surrounding environment of an observer, particularly, a fluorescent lamp or the sun is reflected on a display or the like by being colored in blue, purple, red, or the like. Accordingly, this coloration is an extremely serious problem from the viewpoint, of the visibility of a display or the like.
Further, all of PTLs 1 to 3 have a problem in that the thickness of the retardation plate is extremely thick for a display or the like which is constantly required to be thin because a stretched film having a film thickness of several tens of micrometers is laminated so that the thickness of the retardation plate on which the stretched film is laminated is 150 to 200 μm.
In addition, all of PTLs 1 to 3 also have a problem in that a single wafer system having poor production efficiency must be adopted in a process of laminating a polarizing plate and a retardation plate such that a slow axis of the retardation plate and a transmission axis of the polarizing plate intersect with each other because a stretched film in which a slow axis is fixed in a stretching direction, is used.